Invasive Plant Control at San Juan Island National Historical Park

The North Coast-Cascades Network Invasive Plant Management Team has long partnered with resource management staff to control a suite of weeds at San Juan Island National Historical Park.

San Juan Island National Historical Park in Washington state protects historic areas that tell part of the combined US and United Kingdom history. The park also protects culturally important and rare plants and animals, like blue camas, an important staple for native peoples, and the Island Marble butterfly, a rare species once thought to be extinct. Unfortunately, several invasive plant species threaten the long-term health and existence of these cultural and natural treasures. That’s why the North Coast-Cascades Network Invasive Plant Management Team (NCCN IPMT) works with park staff and Earth Corps youth crew to get rid of invasive plant species.

A Historical Treasure

People have lived on San Juan Island for thousands of years. Ancestors of the native American people arrived around 11,000 years ago. People of European descent moved into the area in the 1800s turning to farming, growing crops and raising livestock on the beautiful dry coastal prairie. This site became San Juan Island National Historical Park, part of the national park system, in 1966 to preserve its thousands of years of cultural and natural history.

Dry Coastal Prairie

The prairie is ideal for farming and raising livestock. Native people used fire to help manage the essential blue camas which they used for food and for other purposes, like making baskets. When farmers, soldiers, and settlers moved from the mainland to the island, they brought non-native plants and animals with them. These new plants posed challenges for native plants by competing for necessary resources. The areas where livestock grazed were perfect places for the invasive plants to grow. Some settlers from European descent also brought along hares, which also disrupted the native ecosystem.

Providing Long-Term Protection

In 2019, NCCN IPMT worked alongside park staff and an Earth Corps youth crew to manually remove several invasive plant species. Then they seeded native plant species over 80 acres among the hills and fields of this historic place. The site, as well as its uncommon array of species, is still threatened by invasive species. NCCN IPMT works closely with San Juan Island National Historical Park staff to develop treatment plans that will meet the cultural and biological needs of the area.